ME-SFI lambda control function - GF07.61-P-4022F

ENGINE 104.941 /943 /944 /991 /994as of 1.8.96 

ENGINE 104.995 with CODE (494a) USA version with CODE (807) Model year 1997 with CODE (808) Model year 1998 with CODE (498) as of Model year 97 Japanese version 

ENGINE 111.921 /942 as of 1.9.98, 111.943, 111.944 as of 1.8.96, 111.946 as of 1.6.98, 111.947 /951 /952 /955 /956 /957 /958 /973, 111.975 as of 1.8.96, 111.982 /983 

ENGINE 111.945 in MODEL 208.335/435 as of 1.6.98, 202.020 /080 as of 1.9.98 

ENGINE 111.974 with CODE (494a) USA version with CODE (807) Model year 1997 with CODE (808) Model year 1998 

ENGINE 112.910 /911 /912 /913 /914 /916 /917 /920 /921 /922 /923 /940 /941 /942 /943 /944 /946 /947 /949 /953 /954 /955 /970 /972 /973 /975 

ENGINE 113.940 /941 /942 /943 /948 /960 /961 /963 /965 /966 /967 /968 /969 

ENGINE 119.980 /981 /982 /985 

ENGINE 120.982/ 983 

ENGINE 137.970 

Shown on Engine 119 

The mixture composition is maintained within the narrowest possible limits around λ =1 in order to achieve a high conversion of the exhaust gases in the catalytic converter.

The O₂ sensor reacts to the oxygen concentration in the exhaust and transmits the corresponding voltage signal to the ME-SFI control unit for fuel injection, which thereupon alters the mixture composition in such a way as to produce a mixture composition of λ = 1 in all operating states when the lambda closed-loop control is active. This procedure is constantly repeated (control loop), the frequency is dependent on engine load and speed. The ME-SFI control unit alters the mixture composition with a time delay in order to prevent any risk of jerking.

The lambda closed-loop control is operational in the following conditions (closed-loop control):

• Coolant temperature < 52° C
• O₂ sensors have reached operating temperature
• Idle speed/part load
• Deceleration fuel shutoff not active.
  Fig 2: Lambda Control Loop Flow Diagram

  

Example: 

Assuming a leaner fuel-air mixture is produced. The consequence of this is that the O₂ sensor voltage tends to move in the direction of 0.1 V and the ME-SFI control unit compensates for this lean drift by enriching the mixture accordingly.

This makes it possible to achieve a fuel-air composition of approximately λ = 1. The readout of the lambda control factor on the HHT alters in the direction +25 %. The more the lambda control factor moves in the direction +25 %, the leaner is the fuel-air mixture and the greater is the enrichment of the mixture on the part of the ME control unit.

Engine 112.946 with code 929 Flexible Fuel Vehicle (FFV) 

After each fueling the Ethanel portion is determined by means of the O₂ sensor voltage upstream TWC in the fuel tank. If for example Ethanol was refueled, the mixture is at first too lean (oxygen sensor voltage jumps back to 0 Volt). The lambda control reacts if the mixture to be enriched until after fueling λ = 1 is achieved again.

	Motor electronics control unit, location/task/design/function	other than engine 111 EVO	GF07.61-P-5000F
		Engine 111 EVO	GF07.61-P-5000GS
	O2 sensors, location/task/design/function		GF07.04-P-4103F
	O2-Sondenheizung Function		GF07.61-P-3025F
	Coolant temperature sensor, location/task/design/function	Engine 119, 120	GF07.04-P-5026F
		Engine 104, 111	GF07.04-P-5026G
		Engine 112, 113, 137	GF07.04-P-5026A
	Self-adaptation of mixture formation function		GF07.61-P-3030F
	Hot film mass air flow sensor, location/task/design/function	Engine 119, 120 (round connector)	GF07.07-P-4118E
		Engine 104, 112, 113, 137 Engine 111 (except engine 111 EVO)	GF07.07-P-4118G
		Engine 111 EVO	GF07.07-P-4118GS
	Pedal value sensor, location/task/design/function		GF30.20-P-4011L
	Fuel injector, location/task/design/function		GF07.03-P-5004F
	ME-SFI two-sensor control function	Engine 104, 111, 112, 113, 119, 120, 137 with EURO3/4 (code 925/926 or standard) and	GF07.61-P-3020F
	Three-way catalytic converter location/task/design/function		GF49.10-P-3002F
	ME Flexible Fuel Vehicle (FFV) function	code 929 Flexible Fuel Vehicle (FFV), engine 112.946	GF07.61-P-3021P